ULA opens 2014 campaign with Atlas V launch of TDRS-L

United Launch Alliance successfully conducted their first mission of 2014 Thursday evening, with an Atlas V deploying NASA’s latest Tracking and Data Relay Satellite, TDRS-L. Liftoff from Cape Canaveral occurred at 21:33 local time (02:33 UTC Friday) mid way through the 40 minute launch window.

Atlas V/TDRS-L Mission:

The twelfth spacecraft in NASA’s Tracking and Data Relay Satellite System (TDRSS), TDRS-L is the second of three third-generation satellites.

It is a 3,454 kilogram (7,615 lb) satellite which was manufactured by Boeing and is based around the BSS-601 satellite bus.

It has a design life of 15 years, however to date most TDRS satellites have significantly exceeded their design expectations. The satellite carries an R-4D-11-300 apogee motor to raise itself into its final orbit and carry out other manoeuvres.

TDRS-L is powered by solar panels, generating between 2.8 and 3.2 kilowatts of power depending on illumination.

The satellite carries s-band phased array antennae to allow simultaneous communications with five other spacecraft, as well as two steerable antennae providing S, Ku or Ka band coverage to spacecraft requiring communications at a higher data rate.

TDRS satellites are used by NASA to provide communications links between spacecraft in orbit – including the International Space Station and Hubble Space Telescope – and ground controllers. Part of NASA’s Space Network, TDRSS was implemented to reduce NASA’s dependence on ground stations and airborne tracking assets.

Use of the network is not restricted to NASA missions; amongst other users United Launch Alliance and Sea Launch both use TDRS to relay data from their rockets during launch, JAXA and the European Space Agency have used TDRS for missions, including HTV and ATV flights to the ISS, and the system is rumoured to be used by the National Reconnaissance Office to supplement its own Satellite Data System, transmitting data from reconnaissance satellites for analysis.

Older satellites in more highly-inclined orbits have been used to relay communications to the Amundsen–Scott Station at the South Pole; a site not usually accessible to communications satellites due to its extreme latitude.

First-generation TDRS satellites were deployed from the Space Shuttle, with an Inertial Upper Stage used to raise them into geostationary orbit. These spacecraft, which were built by TRW, were designed for a seven-to-ten year service life. The first TDRS satellite – TDRS-1 – was deployed during STS-6, the maiden flight of Challenger, in April 1983.

During the launch of TDRS-1 the Inertial Upper Stage malfunctioned. A two-stage solid-fuelled vehicle, the first stage of the IUS performed nominally however during the second stage burn control of the vehicle was lost.

The satellite was deployed into an orbit with a perigee approximately 13,000 kilometres (8,000 mi, 7,000 nmi) below geosynchronous orbit, with its period five and three-quarter hours shorter than expected.

Despite this partial failure the satellite was able to recover to its operational orbit, making a series of firings with its manoeuvring thrusters which gradually raised the perigee over the period of several months. TDRS-1 exceeded its design life almost four times over, finally being decommissioned in June 2010 after its final amplifier failed.

Following the malfunction during the TDRS-1 launch and anomalies on several other flights, concerns over the reliability of the IUS resulted in knock-on delays for the TDRSS programme. STS-12, which had been slated to deploy the second satellite, TDRS-B, was cancelled and the payload reassigned to STS-51-E.

As a result of the failure, the designation TDRS-2, which would have been given to TDRS-B upon the completion of initial on-orbit testing, was never assigned – typically for a programme with separate launch and on-orbit designations in the event of a launch failure the on-orbit designation is reassigned to the next successful mission to avoid gaps in the sequence.

The last first-generation satellite, TDRS-7, was ordered as a replacement for TDRS-B and incorporates some enhancements over the other satellites, while still being based on the same TRW bus.

It was deployed by STS-70 in 1995, and remains in operation at 85 degrees East (275 degrees West) as TDRS-Z, covering the so-called Zone of Exclusion between the operational West and East satellites; TDRS-9 and TDRS-10.

Three second-generation TDRS satellites were built by Hughes Space and Communication, later part of Boeing, and launched between 2000 and 2002. These BSS-601-based spacecraft were launched by Atlas IIA rockets. TDRS-8 was found to have a defective antenna, resulting in reduced performance compared to expectations before launch.

The TDRS-9 and 10 spacecraft suffered from the same fault, however as a result of the problem with TDRS-8 it could be found and corrected while they were still on the ground.

TDRS-9 also suffered from a pressurisation problem in its propulsion system, which resulted in it taking six months to reach its operational orbit. TDRS-9 and 10 are located at 41 degrees and 174 degrees west as the operational TDRS-East and TDRS-West satellites respectively. TDRS-8 is located at 89 degrees east (271 degrees West).

The first two third-generation satellites were ordered in December 2007, with the contract including options for NASA to order two further spacecraft. TDRS-11, known as TDRS-K at the time of launch, was the first third-generation satellite to fly – riding an Atlas V into orbit at the end of January last year.

TDRS-L is the second of the original two orders, while one of the options was exercised in late 2011 at a cost of $289 million. That satellite, TDRS-M, will be launched late next year.

The three primary satellites in the constellation are the TDRS-East, TDRS-West and TDRS-Z satellites; however all of the operable spacecraft aside from TDRS-3 and TDRS-11 are in operational use.

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Once it completes initial on-orbit testing and is handed over to NASA, TDRS-L will be renamed TDRS-12. Several TDRS satellites will be used to support the launch of TDRS-L.

Operationally, these satellites are designated by their longitude; TDRS-275, for example, refers to the satellite at a longitude of 275 degrees west – or 85 degrees east – TDRS-7. The TDRS-49 position will be the first to track the Atlas; while TDRS-3 is located at this slot, it is a backup satellite listed as being in on-orbit storage, so it is more likely that the nearby TDRS-9 satellite, at 41 degrees, will be used instead. At the time of spacecraft separation, the rocket will be in range of the TDRS-275 position.

The rocket which deployed TDRS-L was an Atlas V 401, tail number AV-043. The smallest Atlas V configuration, the 401 variant consists of a single Common Core Booster (CCB) first stage, and a Single-Engine Centaur (SEC) upper stage.

A payload fairing with a diameter of four metres (13 feet) will encapsulate the spacecraft, while no solid rocket motors will be used to augment the first stage’s thrust at liftoff.

The Common Core Booster is powered by a single RD-180 engine, derived from the RD-170 developed by the Soviet Union to power its Zenit rocket. The stage is fuelled by RP-1 propellant, oxidised by liquid oxygen. The Centaur is powered by an RL10A-4-2 engine, which burns liquid hydrogen and liquid oxygen.

The launch of AV-043, which marked the forty-third flight of an Atlas V, began with the ignition of the RD-180 engine at T-2.7 seconds. Its thrust exceeded the mass of the rocket about 1.1 seconds after T-0, allowing the vehicle to rise off the pad and begin its ascent.

Climbing vertically for 16.4 seconds, AV-043 cleared the pad before it began a series of roll, pitch and yaw manoeuvres to place it onto the planned trajectory to achieve geosynchronous transfer orbit.

The rocket flew downrange on a heading of 101.4 degrees, passing through the area of maximum dynamic pressure, or Max-Q, 91.3 seconds after liftoff.

Booster Engine Cutoff, or BECO, marked the end of first stage flight, occurring four minutes and 1.9 seconds into the mission, with the Common Core Booster separating six seconds later.

After staging, the Centaur’s RL10 engine began its prestart sequence; with ignition occurring ten seconds after the spent stage had been jettisoned. Ignition of the Centaur, or Main Engine Start 1 (MES-1), began the first of two planned burns for the upper stage during Thursday’s mission.

The first Centaur burn lasted 13 minutes and 55.1 seconds, with separation of the payload fairing from the nose of the rocket occurring eight seconds after ignition. At the end of the burn, a lengthy coast phase began.

The coast phase lasted an hour, twenty one minutes and 54.7 seconds, before the RL10 ignited again for its second burn. This raised the perigee of the orbit, reducing the amount of fuel TDRS-L must expend to reach its final destination.

By using less fuel at this phase of the mission, TDRS-L will have more available for manoeuvring and stationkeeping, potentially allowing it a longer operational mission.

The second burn lasted 63.1 seconds. Four minutes and 46 seconds after it ended, TDRS-L was separated from the Centaur to begin its own mission. The target orbit for spacecraft separation is a 4,839 by 35,788 kilometres (3007 by 22,238 mi; 2613 by 19,324 nmi) inclined at 25.5 degrees to the equator, with an argument of perigee of 180 degrees.

The launch took place from Cape Canaveral’s Space Launch Complex 41, a site built for Titan III launches in the 1960s.

All East Coast Atlas V launches occur from SLC-41, while Vandenberg Air Force Base’s Space Launch Complex 3E is used for West Coast launches.

Thursday’s launch was the fourth of 2014, the third for the United States and the first of the year for United Launch Alliance and the Atlas V. 2013 was the most successful year for the EELV so far, with eleven launches.

Eight of these were made using Atlas V rockets, including missions to deploy the TDRS-11 satellite, Landsat 8, and NASA’s MAVEN mission to Mars. The final Atlas launch of the year carried NROL-39 (now USA-247), a Topaz radar imaging satellite, and a cluster of CubeSats.

ULA’s next launch is scheduled for 20 February, when a Delta IV will deploy the GPS-IIF-5 navigation satellite. The next Atlas mission will occur in March carrying the NROL-67 payload for the National Reconnaissance Office.